Detecting Linear Dichroism with Atomic Resolution

TL;DR

This paper introduces a novel electron microscopy technique to visualize orbital polarization at atomic resolution, surpassing traditional X-ray methods and enabling detailed studies of electronic anisotropy in quantum materials.

Contribution

The authors develop a versatile electron linear dichroism method in STEM that achieves atomic-scale visualization of orbital occupation, validated against X-ray measurements.

Findings

Resolved Mn-3d eg orbital polarization with sub-angstrom precision.

Demonstrated strain-dependent stabilization of orbital occupation.

Validated method against established X-ray dichroism results.

Abstract

X-ray linear dichroism has been pivotal for probing electronic anisotropies, but its inherent limited spatial resolution precludes atomic-scale investigations of orbital polarization. Here we introduce a versatile electron linear dichroism methodology in scanning transmission electron microscopy that overcomes these constraints. By exploiting momentum-transfer-dependent electron energy-loss spectroscopy with an atomic-sized probe, we directly visualize orbital occupation at individual atomic columns in real space. Using strained La0.7Sr0.3MnO3 thin films as a model system, we resolve the Mn-3d eg orbital polarization with sub-angstrom precision. We show that compressive strain stabilizes 3z2-r2 occupation while tensile strain favors x2-y2. These results validate our approach against established X-ray measurements while achieving the ultimate single atomic-column sensitivity. We further demonstrate two optimized signal extraction protocols that adapt to experimental constraints without compromising sensitivity. This generalizable platform opens unprecedented opportunities to study symmetry-breaking phenomena at individual defects, interfaces, and in quantum materials where atomic-scale electronic anisotropy governs emergent functionality.